The correct answer to this open question is the following.
The power of Congress that Senator Paul probably most concerned about based on this passage is the Power to Declare War.
The United States Constitution states on Article I, section clause 1, that the United States Congress has the power to declare war. The Constitution grants Congress with expressed powers and this is one of them. That is why Senator Rand Paul is reflecting on the great responsibility Congress has regarding thus power of declaring war against another nation.
Nelson Mandela helped end apartheid, so A is incorrect. B would be right, but the white population is the minority in South Africa, not the majority. It ended in 1991, so C is not right. This leaves us with D, the correct answer. I hope this helps!
In regard to gender issues in sub-Saharan Africa, generally speaking "<span>d. Women had more opportunities open to them than did their counterparts in other societies," although this depended slightly on the specific region and time in question. </span>